Showa Separate Function Triple Chamber Atmosphere Fork Explained!

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Inside the Showa SFF-AIR TAC Front Suspension


By Scot Gustafson and Chris Denison

Photos by Adam Campbell

The Showa SFF-AIR TAC front suspension is new at the 2015 Kawasaki KX450F and, although confusing at first, the new setup isn’t all that hard to understand once explained. First off, SFF/ TAC stands for Separate Function Shell and Triple Air Chamber. While the fork looks and sounds complicated, the design is very simple. The most complicated component is trying not to be redundant by calling it an SFF Shell. Similar to saying ATM Machine (Automatic Teller Machine Machine), it’ s i9000 not a Separate Function Fork Shell!

SFF means Individual Function Fork because each shell leg performs a separate function. The left leg contains the damping cartridge and the right fork leg provides the pneumatic air spring. TAC indicates Triple Air Chamber. The right shell leg houses three pneumatic air flow chambers to tune the air springtime side of the fork. The advantages of this particular fork are adjustability, weight, and minimal effect on total pressure if the fork leg and seal are damaged. The air spring allows cyclists of all sizes to be able to set up their bikes at the track without any disassembly or costly fork springs. Additionally , air pressure can be altered rapidly when track conditions change along with mud, hard pack, rocks and loamy soil. The Showa shell weighs almost a pound less than last year’s air fork and two to three pounds less than a spring shell. Fork damage has less impact this year because the outer chamber from the Triple Air Chamber that is next to the fork seal holds very little air (about seven psi) and produces less force than the other two chamber that are typically established at 130 and 145 p.s.i., respectively.

The remaining fork leg handles the dissipating duties for the entire fork. Adjustment is with standard compression adjusters on top and rebound adjusters on the bottom. The first thing you notice is everything inside the shell is huge when compared to a typical double chamber fork. The Base Valve stud is 12mm, making the data compresion valving shims the same size as most rear shocks. The Oil Locking mechanism Collar-Bottoming Cone is enormous and the damper rods are 14mm when compared to typical 12. 5mm. Also bigger this year is the fork leg diameter, which has been increased to 49mm.

The right fork leg houses the Triple Air Chamber. On top of the fork are two air flow valves that charge the inner and outer chambers of the shell. The outside chamber is low pressure with the standard setting 7 p.s.i. that can range from 0-19 psi. The inner chamber looks like a normal shell cartridge and is typically set at 145 psi but can range from 87-189psi. The inner cartridge keeps most of the fork’s total force. The unique looking attachment on the bottom from the fork is the balance chamber. The balance chamber works to push against the 2 air chambers on top to help obtain the fork in motion. Without this particular negative pressure the fork will be harsh because it would take a huge bump to get the air fork to relocate. Last year, the KYB fork had a balance spring inside the fork cartridge to help counteract the force from the air. That spring was really labor-intensive to change so it could not become fine-tuned anytime the air pressure has been varied. On the new fork, the balance chamber is typically set at 140 psi and can range from 77-203 p.s.i.. Adding more air to the balance chamber helps get the fork in motion and makes it more compliant to small bumps. Adding too much air flow will draw the fork down and make it ride low therefore the key is to balance the bicycle so the fork will maintain an appropriate ride height and still be little bump compliant. Showa suggests that you change the high-pressure chambers in 7-14 lbs. increments. The 2015 KX450F comes stock with a 0-300 p.s.i. digital pump from Kawasaki. Curiously enough, it takes 2 psi to fill the gauge head and pump hose, so there is a little bit of science to adding air. Kawasaki strongly recommends that you do not fill the fork from a tank, as extra moisture can get inside of the fork and ruin your day.

As of right now, we have only spent one full day on the new shell, but we are looking forward to really searching in and doing some extensive assessment with the new SFF-Air. Do the stresses vary greatly with temperature/ driving time? What is the best setting? How can it react off-road? These are almost all questions that we will be asking, although after the first day aboard this particular fork it was clear that the huge adjustability makes for a huge number of variables. We were able to find a decent environment, but even the Kawasaki technicians by themselves admitted that they are still figuring out the simplest way to utilize this new tool. Keep your eye open for the full test from the Kawasaki KX450F in an upcoming issue of Dirt Driver , as well as for further testing notes and findings as we dig into this fork in the near future. In the meantime, check out this video for additional info on the Showa SFF-Air TAC setup!

The negative/ balance chamber on the air fork provides negative pressure to the fork, actually pulling it down more as air is increased.

The negative/ balance chamber on the air shell provides negative pressure to the shell, actually pulling it down more as air is increased.

On the track, the SFF-Air has a more plush feeling than we expected, with easier bottoming and a softer stock stroke than the KYB setup from 2014.

For the track, the SFF-Air has a more plush feeling than we anticipated, with easier bottoming and a smoother stock stroke than the KYB setup from 2014.

The two air fill valves at the top handle the outer (camera left/ grip side) and inner (camera right/ clamp side) chambers, respectively.

The two air fill up valves at the top handle the external (camera left/ grip side) and inner (camera right/ clamp side) chambers, respectively.

A cutaway view of the fork shows the air chambers in the right (camera left) side, and the beefy valving in the left (camera right) fork leg.

A cutaway see of the fork shows the air chambers in the right (camera left) aspect, and the beefy valving in the remaining (camera right) fork leg.

Although complicated at first, understanding the new SFF-Air function is fairly simple once you wrap your head around it.

Although complicated at first, understanding the new SFF-Air function is fairly simple once you cover your head around it.

The Showa SFF-Air TAC is the biggest new change to the 2015 Kawasaki models.

The Showa SFF-Air TAC is the biggest new change to the 2015 Kawasaki models.

 


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